Automotive engines use a closed or positive crankcase ventilation (PCV) system to insure that harmful vapors do not escape into the environment. A typical prior art PCV system is shown in FIG. 1. The PCV system establishes a direct flow path from the engine crankcase to the intake manifold to insure positive ventilation. Flow is induced by the differential pressure between the intake manifold and the crankcase. Total flow through the PCV system is made up of fresh air (where supplied), blow-by past piston rings, and a mist of oil, water, and gasoline from the crankcase. Testing has shown that a substantial amount of oil can be contained in the PCV gas flow; and that the level of oil being consumed through the PCV system is a significant contributor to overall oil consumption in many engines.
A number of patents have been issued for devices used to remove liquid from PCV gases or gases originating from the engine crankcase. Namiki et al U.S. Pat. No. 4,627,406 uses offset baffles and a barrier, coalescing filter to remove liquid from the PCV gas stream. Katoh et al. U.S. Pat. No. 4,502,424 uses baffles with double outlets from the crankcase to insure ventilation under extreme engine angles. Gates Jr. et al. U.S. Pat. No. 4,401 093 uses a labyrinth plus barrier filter at the oil fill/breather cap to remove liquid. Walker U.S. Pat. No. 4,269,607 uses reverse flow and varying flow areas to remove liquid from gas in the PCV system. Bush U.S. Pat. No. 4,089,309 uses baffles plus a glass bead screen to separate liquid from PCV gas. Lipscomb U.S. Pat. No. 3,877,451 uses a barrier filter for removal of liquid from PCV gas. Otofy U.S. Pat. No. 4,765,386 is based on the use of a wire mesh barrier filter. An earlier patent by Walker U.S. Pat. No. 3,721,069 uses baffling with a barrier filter. Bruenn U.S. Pat. No. 3,299,873 uses a labyrinth and baffles for the same purpose. Jackson U.S. Pat. No. 3,179,097 uses a labyrinth to "precipitate" oil out of a system designed to modulate crankcase pressure or vacuum. Henderson U.S. Pat. No. 3,088,447 feeds crankcase vapors through a needle valve and barrier filter to an electrically heated screen below the carburetor for vaporization and subsequent combustion. Beckett U.S. Pat. No. 2,604,186 controls crankcase gas flow with a variable orifice device which is protected by a barrier filter. Schreurs U.S. Pat. No. 2,041,435 separates liquid from vaporized fuel at the carburetor inlet with a brass barrier filter and baffling. Tracy U.S. Pat. No. 1,427,337 uses a baffled, vacuum controller to regulate crankcase flow to the intake manifold.
In all of these patents, the technique used to separate liquid from gas is either baffles, barrier filters, labyrinths, or a combination of these. None of the patents uses precise, scientific design techniques to configure an inertial impactor for separation based on particle or droplet size. In general, baffles or labyrinths will have low filtration efficiency. Barrier filters can produce high filter efficiency but require more space to accomplish this with low restriction. Increased size makes packaging the filter around the engine more difficult. Barrier filters contain filter elements which are subject to plugging and icing; and must be cleaned or changed at frequent intervals.
None of the patents recognizes the need to prevent fuel and water from being collected with the oil; and none suggests the use of heat to condition the incoming sample so that oil is collected and fuel and water are not.
Accordingly, among the objectives of the present invention are to provide a PCV oil separator system wherein oil particles are separated from the PCV flow while fuel and water particles pass on through the system to re-enter the engine; wherein the modification to the conventional PCV oil separator system is minimal; wherein the modification may be made at low cost.
In accordance with the invention, the positive crankcase ventilation system includes an oil separator positioned adjacent the engine such that the oil separator is subjected to a predetermined minimum operating temperature. The oil separator comprises an opening through which the oil, fuel and water particles pass in the PCV gas flow. The oil separator is constructed and arranged to cause the oil particles to strike an impactor plate and to be separated from the gas flow while fuel and water particles pass on through the system and reenter the engine.